The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Referring now to FIG. 1, a functional block diagram of a vehicle powertrain 100 according to the prior art is presented. The vehicle powertrain 100 includes an engine 102 that generates drive torque. Air is drawn into an intake manifold 104 of the engine 102 through a throttle 106. Operation of the engine 102 is monitored and controlled by a control module 110.
The control module 110 receives signals from a MAP (Manifold Absolute Pressure) sensor 112 in the intake manifold 104, a throttle position sensor 114, a MAF (Mass Air Flow) sensor 116, and other sensors (not shown). The control module 110 controls various functions of the engine 102, including opening and closing the throttle 106. The control module 110 receives driver input from, for example, an accelerator pedal position sensor 120.
The control module 110 also receives input from vehicle control systems, such as a cruise control module 122, a stability control system (not shown), a traction control module (not shown), etc. The control module 110 determines the desired engine torque based upon the inputs. The control module 110 instructs the throttle 106 to open to a specified position to allow a desired airflow into the engine 102 to produce that desired engine torque.
The control module 110 may use a mapping from desired airflow to throttle area opening to determine the desired throttle area opening. The control module 110 may then use a mapping from throttle area opening to throttle position to determine where to position the throttle 106. The relationship between desired throttle area opening and throttle position may change over time. For example, deposits may accumulate on the throttle 106, especially in applications where vehicle drive times are short.
The accumulation of deposits on the throttle 106 is sometimes referred to as coking. To compensate for such changes, a Learned Airflow Variation Algorithm (LAVA) has been disclosed in commonly assigned U.S. Pat. Nos. 7,024,305 and 6,957,140, the disclosures of which are hereby incorporated by reference in their entirety. In various implementations, the LAVA provides for two tables that each include a mapping from uncompensated throttle area to throttle area correction factor.
The throttle area correction factor may be added to the uncompensated throttle area to produce a compensated throttle area. The compensated throttle area can then be mapped to a throttle blade position for the throttle 106. The throttle area correction factor may be negative when an empirically determined throttle area opening is larger than expected for a given throttle position. The two tables may be an upper table and a lower table, corresponding to larger uncompensated area values and smaller uncompensated area values, respectively.
The upper and lower tables may include mutually exclusive ranges of uncompensated throttle area or may overlap at one or more uncompensated throttle area values. The upper and lower tables may each have a predetermined upper limit for the amount of throttle area correction. The control module 110 may update the upper and lower tables to reflect changes in effective throttle area opening based upon airflow data from the MAP sensor 112 and the MAF sensor 116.